Machine for anticipatory sensing and intervention to avoid swimmer entrapment

ABSTRACT

A machine for anticipatory sensing and intervention to avoid swimmer entrapment, with an active pre-entrapment sensor (e.g. ultrasonic) that assesses the relative hazard based on swimmer proximity to the drain cover. An Ultrasonic Transducer launches waves into the suction piping and/or drain system, and to receive echoes from the drain cover, swimmer limbs, hair or body, and the water surface parellel to the drain cover. A Transmitter/Pulser electrically energizes the ultrasonic transducer to launch waves into the suction piping and/or drain system, A Receiver/Processor detects the echoes electrical signals from the the ultrasonic transducer and to receive echoes from objects of interest beyond the pool drain. A Logic and Control element converts the detected signals into reliable information regarding a swimmer safety/hazard status. An Output provides a pump shutdown command when required. Solutions for both new construction and retrofit are described.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on provisional application Ser. No. 60/549514,filed on Mar. 2, 2004 and provisional application Ser. No. 60/587367,filed on Jul. 13, 2004.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

DESCRIPTION OF ATTACHED APPENDIX

Not Applicable

BACKGROUND OF THE INVENTION

This invention relates generally to the field of Swimmer EntrapmentAvoidance and more specifically to a machine for anticipatory sensingand intervention to avoid swimmer entrapment.

Entrapment comprises all of the hazards of evisceration, hairentanglement, limb entrapment, body entrapment, etc.

To provide a means of detecting the required presence of the draincover, the absence of which creates a lethal hazard. A missing draincover requires immediate pump shutdown and no existing SVRS system candetect this situation.

To provide a means of anticipating a potential swimmer entrapmentsituation as at a swimming pool or spa drain.

The present invention utilizes an active sensor technology that allowsanticipatory sensing and intervention before hazardous drain contact canoccur.

The Consumer Product Safety Commission (CPSC) has reported over manyyears that there are dozens of deaths and grave injuries each year inthe US, mostly young children, due to the suction entrapment hazards ofswimming pools, wading pools and spas. The CPSC has recently set uptesting facilities for Safety Vacuum Release Systems (SVRS), productsnow on the market intended to rapidly reduce suction and release anentrapped person. The potential and actual hazards due to underwatersuction drains include disembowelment (which can occur in a fraction ofa second), hair entanglement, and limb or body entrapment. All SVRSdevices now sense an increase in suction, near the pump inlet, thatoccurs when a person blocks all or a major part of a remote suctiondrain. None can anticipate the event, and that is a serious flaw inswimmer protection.

In addition to the tragic results mentioned there are large societalcosts related to long term medical treatment of the injured, majorawards and expenses of litigation, inhibiting business activity, andreducing opportunity for the public to enjoy the fitness, health andrecreation benefits of safe water facilities whether public or private.

This invention can deal with new construction as well as retrofit, butthe overwhelming market for industry lies in the estimated 15 million ormore old swimming pools that can not feasibly be retrofitted with priortechnology. Moreover, it is precisely these old pools that are the mosthazardous because they do not have the other safety features such asanti-entrapment, anti-entanglement drain covers, dual main drains,vents, or SVRS devices that are now increasingly found on new pools. Oldpools may also have been upgraded with higher power pumps that present astronger suction hazard. Present SVRS also have a major weakness interms of field reliability over years of time with no requirements forperiodic testing and traceability of such tests. In addition, theproposed solution may also be useful for new construction as well.

The object of this invention is to provide swimmer protection whereinthe occurrence of a potentially or actually hazardous approach to adrain is measured and can be acted upon prior to any contact orentrapment occurring. FIG. 1 depicts a typical situation.

The objective is to use the pool suction piping network as asonic/ultrasonic waveguide. If a sonic pulse wave is launched into thesuction piping network from a point above ground, near the pump inlet,propagates through the suction piping network to the underwater plasticdrain cover(s) (they may be augmented) and provides a unique return echoso that we can be assured that the drain cover is in place. This is amajor benefit because missing drain covers have produced horrendouspermanent injuries and drownings.

Futhermore, the sonic pulse wave will also pass thru the cover, and/orits holes for the passage of water, and detect the pool water/airinterface which is a strong reflector. This allows for a self-testingand self-calibrating sensor system. In addition, a swimmer approaching adrain can be sensed directly and/or indirectly by means of simple rangegating since the geometry is fixed for any given existing pool. Thefollowing figure depicts a situation where the transducer is co-locatedwith a drain, but the principle is equally applicable for a transducerlocated far from the drain by means of a low loss sonic/ultrasonicwaveguide.

Another benefit of an active sonic sensor is the potential to measurethe water velocity in the suction piping via doppler processing.Excessive water velocity is indicative of issues such as a replacementpump of higher horsepower than is safe for the original installation.

Also, as in FIG. 1, sensing of excessively high or low pool water levelwill also be feasible.

Ultrasonics is a rapidly advancing technology with a high degree of newknowledge and understandings with many new applications. The literatureis replete with examples of rapid variations of attenuation withfrequency for certain modes of propagation. U.S. Pat. No. 5,289,436Ultrasonic waveguide, J. H. Terhune offers some interesting examples oflow loss frequency windows in thin tubular structures. Such frequencywindows are exploited in the present invention.

The state of the art in piping networks is based on steel piping overmedium to long spans where the object is to detect flaws (e.g corrosion)from a distance because the piping is inaccessable. That technique hasproven sucessful and is commercialized.

This invention addresses plastic piping, and specifically PVC piping andstandard PVC fittings because that is what is to be found in the vastmajority of existing swimming pools. And, of course, the piping liesunderground and sometimes under the pool structure which is most oftenpoured concrete. New pool construction has fewer constraints on materialchoices and access for optimization is available. The research leadingto this invention has shown useful, low loss, windows in the frequencydomain that allow the application to be realized commercially.

All SVRS devices now sense an increase in suction, near the pump inlet,that occurs when a person blocks all or a major part of a remote suctiondrain. None can anticipate the event, and that is a serious flaw inswimmer protection.

FIELD OF THE INVENTION

The present invention relates generally to entrapment avoidance sensorsand more specifically it relates to aanti-evisceration/entanglement/entrapment sensor system for a solutionto the suction drain entrapment and entanglement hazard found in mostswimming pools, spas and hot tubs. When a pool drain cover is damaged ormissing a major hazard for limb or body entrapment, and evenevisceration, exists. The ability of this invention to sense a missingdrain cover is unique and can be used to shutdown the circulation systemand generate alarms. The capability for short range swimmer detection isunique and extremely valuable because prevention of entrapment has beenshown to be much safer than release of entrapment after it occurs. Thisis particularly true for situations leading to evisceration or hairentanglement.

Several Existing Patents Cover SVRS and Related Devices:

Recently, a few single purpose suction safety devices have been broughtto market. A few single purpose pump suction sensor and shut-downdevices and systems have also been brought to market such as: StinglSwitch, 6,059,536, Stingl, May 9, 2000; and Influent Blockage DetectionSystem, U.S. Pat. No. 6,342,841, January 2002, Stingl; and Fluid VacuumSafety Device for Fluid Transfer Systems in Swimming Pools, 5,947,700,September 1999, McKain et al; and Spa Pressure Sensing System Capable ofEntrapment Detection, U.S. 6,227,808, May 2001, McDonough.

Several other patents describe very specific capability for a singlepurpose using novel sensors. For example: Pump Shutoff System,6,039,543, March 2000, Littleton; describes a flow switch and controlcircuit to shut-down a pump when there is insufficient fluid flow andpump damage may result. Also, Pool Pump Controller, 5,725,359, March1998, Dongo et al; does address swimmer safety regarding suctionentrapment in a pool drain, by means of a novel diaphragm switch thatremoves power from the pool pump when a certain change in fluid pressure(unspecified) occurs.

Deficiency in Prior Technology

Some other prior art deficiencies may be summarized by the following:

-   -   A few specialized pump suction sensor switches e.g. Stingl        Switch, 6,059,536, Stingl, May 9, 2000, and Influent Blockage        Detection System, U.S. Pat. No. 6,342,841, January 2002, Stingl.        These are expensive single purpose devices marketed primarily to        municipal and large club pools. The MIMPSC, U.S. Pat. No.        6,676,831, however, is intended primarily for residential pools        and spas where cost is a significant factor. If certain cost        targets and multi functionality cannot be provided, most        residential pools will continue to be unprotected, with        concomitant risks to users and equipment.

Suction safety requires fast, sure removal of the entrapment force,severely limiting both the magnitude and duration of that force. Hairentanglement hazards are possibly quite sensitive to the duration of thesuction force as well. Stingl, U.S. Pat. No. 6,342,841 asserts “there isno need to “relieve” residual vacuum in the line because water is notcompressible”. The MIMPSC invention asserts, however, that there is avery significant increase in the total impulse (force×time) causingentrapment of a person. Recent data from an actual pool installationwith the present invention showed a small increase in peak force of12.3%, but accompanied by a large increase in the action time. The totaltime of significant entrapment force, as measured from the beginning ofa measured rise in suction to when the shut-down returned suction to itsbeginning level was: With suction dump valve: 0.417 seconds Withoutsuction dump: 1.503 seconds

This is a ratio of 3.6 to 1. Multiplying the force and time ratios wefind that the overall entrapment impulse is four times greater if we donot “relieve” the suction with a vent to atmospheric pressure. Theexplanation for this situation may be related to the fact that thesuction water column and pump impeller momentum does not instantlydisappear when power is shutoff, but dissipates over a time period of1.5 seconds. In the above discussion, just as in the cited patent, themeasured suction was at or near the pump inlet port. Furthermore, if weexamine the ratio of entrapment or entanglement time starting from whenthe pump is shutoff we find that:

Time from Shutoff to Atmospheric Pressure: With Suction Dump Valve: 0.08seconds Without Suction Dump: approximately 4 seconds

This is considered to be reason enough to include suction relief byusing a properly configured dump valve. The cited patent also describesa “safe level of vacuum as 11 in.Hg.”. This level of vacuum isconsidered too high by several authorities, especially if prolongedaction time is involved. The MIMPSC invention also accounts for theminor variations present in pools with in floor cleaning systems andsolar heating, but typically operates at a shut-down threshold of 8in.Hg.

Another patent, 5,947,700, September 1999, McKain et al, describes analternative embodiment of a suction entrapment release device, andmentions that the “ideal vacuum pressure at which the frangible memberdisintegrates is approximately 20 in. Hg.” This value is consideredextraordinarily high as a safe limit. In fact, it is questionable as towhether it could be achieved at the location shown, near the input tothe pump, because of the presence of the second suction line from thepool.

The main problem with conventional entrapment avoidance sensors are thatthey are constrained to allow a significant increase in the suctionhazard before taking corrective action. This allows a potential victimto approach the drain closely without a significant increase in thesuction being sensed. Only when the suction port is mostly blocked bythe victims body or limb does a large increase in suction suddenlyoccur. Under these conditions a small child may be partially or totallyeviscerated in an extremely short period of time. Some tests reported inthe literature indicate that damage can be done within a small fractionof a second, when the short distance to complete the drain sealing iscovered and a very high degree of vacuum is thereby allowed to occurmomentarily. Another problem with conventional entrapment avoidancesensors are that they cannot anticipate the dangerous level of suctionwhich will occur with full drain blockage until it occurs. The subjectinvention directly senses and measures the approach of a person or otherobject to the drain before significant blockage can occur. Thisanticipation by the subject invention is due to sensing distance fromthe drain rather than the consequence of a blocked drain. Anotherproblem with conventional entrapment avoidance sensors are that theycannot detect the missing drain cover. When a drain cover is missing thestage is set for limb entrapment leading to drowning or as in severalcases a lifelong mental disability due to prolonged oxygen starvation.Only an active sensor operating at close range from within the drainsystem can easily and surely detect and prevent all five major forms ofdrain entrapment as defined in ASME A112.19.17-2002, ASTM PS 10-03, andNSPI X(in work).

While these devices may be suitable for the particular purpose whichthey address, they are not as suitable for a solution to the suctiondrain entrapment and entanglement hazard found in most swimming pools,spas and hot tubs. When a pool drain cover is damaged or missing a majorhazard for limb or body entrapment, and even evisceration, exists. Theability of this invention to sense a missing drain cover is unique andcan be used to shutdown the circulation system and generate alarms. Thecapability for short range swimmer detection is unique and extremelyvaluable because prevention of entrapment has been shown to be muchsafer than release of entrapment after it occurs. This is particularlytrue for situations leading to evisceration or hair entanglement. Themain problem with conventional entrapment avoidance sensors are thatthey are constrained to allow a significant increase in the suctionhazard before taking corrective action. This allows a potential victimto approach the drain closely without a significant increase in thesuction being sensed. Only when the suction port is mostly blocked bythe victims body or limb does a large increase in suction suddenlyoccur. Under these conditions a small child may be partially or totallyeviscerated in an extremely short period of time. Some tests reported inthe literature indicate that damage can be done within a small fractionof a second, when the short distance to complete the drain sealing iscovered and a very high degree of vacuum is thereby allowed to occurmomentarily. Another problem is that they cannot anticipate thedangerous level of suction which will occur with full drain blockageuntil it occurs. The subject invention directly senses and measures theapproach of a person or other object to the drain before significantblockage can occur. This anticipation by the subject invention is due tosensing distance from the drain rather than the consequence of a blockeddrain. Also, another problem is that they cannot detect the missingdrain cover. When a drain cover is missing the stage is set for limbentrapment leading to drowning or as in several cases a lifelong mentaldisability due to prolonged oxygen starvation. Only an active sensoroperating at close range from within the drain system can easily andsurely detect and prevent all five major forms of drain entrapment asdefined in ASME A112.19.17-2002, ASTM PS 10-03, and NSPI X(in work).

In these respects, the anti-evisceration/entanglement/entrapment sensorsystem according to the present invention substantially departs from theconventional concepts and designs of the prior art, and in so doingprovides an apparatus primarily developed for the purpose of a solutionto the suction drain entrapment and entanglement hazard found in mostswimming pools, spas and hot tubs. When a pool drain cover is damaged ormissing a major hazard for limb or body entrapment, and evenevisceration, exists. The ability of this invention to sense a missingdrain cover is unique and can be used to shutdown the circulation systemand generate alarms. The capability for short range swimmer detection isunique and extremely valuable because prevention of entrapment has beenshown to be much safer than release of entrapment after it occurs. Thisis particularly true for situations leading to evisceration or hairentanglement.

All SVRS devices now sense an increase in suction, near the pump inlet,that occurs when a person blocks all or a major part of a remote suctiondrain. None can anticipate the event, and that is a serious flaw inswimmer protection.

This invention can deal with new construction as well as retrofit, butthe overwhelming market for industry lies in the estimated 15 million ormore old swimming pools that can not feasibly be retrofitted withpresent technology. Moreover, it is precisely these old pools that arethe most hazardous because they do not have the other safety featuressuch as anti-entrapment, anti-entanglement drain covers, dual maindrains, vents, or SVRS devices that are now increasingly found on newpools. Old pools may also have been upgraded with higher power pumpsthat present a stronger suction hazard. Present SVRS also have a majorweakness in terms of field reliability over years of time with norequirements for periodic testing and traceability of such tests. Inaddition, the proposed solution may also be useful for new constructionas well.

With the present invention we can be assured that the drain cover is inplace. This is a major benefit because missing drain covers haveproduced horrendous permanent injuries and drownings.

The present invention relates generally to entrapment avoidance sensorsand more specifically it relates to aanti-evisceration/entanglement/entrapment sensor system for a solutionto the suction drain entrapment and entanglement hazard found in mostswimming pools, spas and hot tubs. When a pool drain cover is damaged ormissing a major hazard for limb or body entrapment, and evenevisceration, exists. The ability of this invention to sense a missingdrain cover is unique and can be used to shutdown the circulation systemand generate alarms. The capability for short range swimmer detection isunique and extremely valuable because prevention of entrapment has beenshown to be much safer than release of entrapment after it occurs. Thisis particularly true for situations leading to evisceration or hairentanglement.

The main problem with conventional entrapment avoidance sensors are thatthey are constrained to allow a significant increase in the suctionhazard before taking corrective action. This allows a potential victimto approach the drain closely without a significant increase in thesuction being sensed. Only when the suction port is mostly blocked bythe victims body or limb does a large increase in suction suddenlyoccur. Under these conditions a small child may be partially or totallyeviscerated in an extremely short period of time. Some tests reported inthe literature indicate that damage can be done within a small fractionof a second, when the short distance to complete the drain sealing iscovered and a very high degree of vacuum is thereby allowed to occurmomentarily.

Another problem with conventional entrapment avoidance sensors are thatthey cannot anticipate the dangerous level of suction which will occurwith full drain blockage until it occurs. The subject invention directlysenses and measures the approach of a person or other object to thedrain before significant blockage can occur. This anticipation by thesubject invention is due to sensing distance from the drain rather thanthe consequence of a blocked drain. Another problem with conventionalentrapment avoidance sensors are that they cannot detect the missingdrain cover. When a drain cover is missing the stage is set for limbentrapment leading to drowning or as in several cases a lifelong mentaldisability due to prolonged oxygen starvation. Only an active sensoroperating at close range from within the drain system can easily andsurely detect and prevent all five major forms of drain entrapment asdefined in ASME A112.19.17-2002, ASTM PS 10-03, and NSPI X(in work).

In these respects, the anti-evisceration/entanglement/entrapment sensorsystem according to the present invention substantially departs from theconventional concepts and designs of the prior art, and in so doingprovides an apparatus primarily developed for the purpose of a solutionto the suction drain entrapment and entanglement hazard found in mostswimming pools, spas and hot tubs. When a pool drain cover is damaged ormissing a major hazard for limb or body entrapment, and evenevisceration, exists. The ability of this invention to sense a missingdrain cover is unique and can be used to shutdown the circulation systemand generate alarms. The capability for short range swimmer detection isunique and extremely valuable because prevention of entrapment has beenshown to be much safer than release of entrapment after it occurs. Thisis particularly true for situations leading to evisceration or hairentanglement.

BRIEF SUMMARY OF THE INVENTION

The primary object of the invention is to prevent Entrapment whichcomprises all of the hazards of evisceration, hair entanglement, limbentrapment, body entrapment, etc.

Another object of the invention is to provide a means of detecting therequired presence of the drain cover, the absence of which creates alethal hazard. A missing drain cover requires immediate pump shutdownand no existing SVRS system can detect this situation.

Another object of the invention is to provide a means of anticipating apotential swimmer entrapment situation as at a swimming pool or spadrain.

A further object of the invention is anticipate a potential entrapment.Present Safety Vacuum Release Systems (SVRS) can do nothing toanticipate an entrapment until physical contact is made with the drainor drain cover and a significant increase in suction is sensed.

Yet another object of the invention is to avoid the risk of eviscerationwhich is an extremely rapid process, as is hair entanglement, and thedamage is done before present SVRS devices can react to the hazard.

Still yet another object of the invention is to utilize an active sensortechnology that allows anticipatory sensing and intervention beforehazardous drain contact can occur.

Another object of the invention is to detect masking of the watersurface echo by any absorbtive object that may also be treated as analarm situation.

Another object of the invention is to provide solutions for the twocategories of need for the present invention: New pool/spa construction,and retrofit for old, existing, pool/spas.

A further object of the invention is that the optimum sensors may bedifferent for each category because in new construction there are fewerconstraints on operating frequency, transmitter power and receiversensitivity, which control object detection, resolution and maximumrange.

Yet another object of the invention is, for new construction, tooptimize the suction piping network by eliminating the attenuative 90degree elbows, using larger bend radius sweep elbows.

Still yet another object of the invention is, for new construction,locating a sensor in or under/behind each drain and the beams are easilydirected perpendicular to the drain cover and beyond to the swimmingarea. Thus, the presense of an approaching swimmer can be detected, andtracked, to allow the pump to be shutdown prior to a dangerous physicalcontact.

Another object of the invention is, for existing pools, retrofittingdrains and thus different frequencies and modes can be considered forpropagation through the suction piping network.

Another object of the invention is a flow rate sensor. Flow is asignificant parameter in the design of swimming pools and is not usuallyverified in the field. The sensor system can be enhanced to measure thedoppler shift or Time of Flight, and thus provide a good estimate ofwater speed in the piping. The ANSI/ASME standards for water velocityare established to insure that the velocity is low enough to limit themagnitude of the suction hazard, and high enough for an economical pumpand piping design. Additionally, low water velocity may be a symptom ofa partially blocked drain or filter and can be used to alert servicepersonnel.

A further object of the invention is the further benefit of a poolalarm, for example if a child falls into the pool, it is possible todetect this by various sensor modifications and/or extensions.

Yet another object of the invention is to provide an innovative designthat is also self testing and self calibrating, unlike any other SVRS.

Other objects and advantages of the present invention will becomeapparent from the following descriptions, taken in connection with theaccompanying drawings, wherein, by way of illustration and example, anembodiment of the present invention is disclosed.

In accordance with a preferred embodiment of the invention, there isdisclosed a machine for anticipatory sensing and intervention to avoidswimmer entrapment, comprising: An active suction entrapment sensor(e.g. ultrasonic) that can assess the relative hazard based on swimmerproximity to the drain cover, An Ultrasonic Transducer, one or more, tolaunch waves into the suction piping and/or drain system, and to receiveechoes from the drain cover, swimmer limbs, hair or body, and the watersurface above the drain, A Transmitter/Pulser to electrically energizesaid ultrasonic transducer to launch waves into the suction pipingand/or drain system, A Receiver/Processor to detect the echoeselectrical signals from the said ultrasonic transducer, and to receiveechoes from objects of interest beyond the pool drain, including but notlimited to, the drain cover, a swimmer's body or limb in close proximityto the drain and/or cover, and the pool water surface, A Logic andControl element to convert the detected signals into reliableinformation regarding a swimmer safety/hazard status., An Output toprovide a pump shutdown command if a close approach by a swimmer near adrain is measured, A housing for the Transmitter and Receiver, Logic andControl that can be located in the pool equipment area, near the pumpinlet piping. A transducer mounting and interface adjacent to the pumpinlet suction piping for retrofit applications. The transducer and itsinterconnecting cable may be mounted in or under the drain for newconstruction, or the same as for retrofit if suitable, and for newconstruction, and in some cases for retrofit, other suction side pipingand fittings that optimize performance may be used instead of theSchedule 40 90 degree elbow that has been the standard for some time.

In accordance with a preferred embodiment of the invention, there isdisclosed a process for anticipatory sensing and intervention to avoidswimmer entrapment, comprising the steps of: An active suctionentrapment sensor (e.g. ultrasonic) that can assess the relative hazardbased on swimmer proximity to the drain cover, An Ultrasonic Transducer,one or more, to launch waves into the suction piping and/or drainsystem, and to receive echoes from the drain cover, swimmer limbs, hairor body, and the water surface above the drain, A Transmitter/Pulser toelectrically energize said ultrasonic transducer to launch waves intothe suction piping and/or drain system. A Receiver/Processor to detectthe echoes electrical signals from the said ultrasonic transducer, andto receive echoes from objects of interest beyond the pool drain,including but not limited to, the drain cover, a swimmer's body or limbin close proximity to the drain and/or cover, and the pool watersurface, A Logic and Control element to convert the detected signalsinto reliable information regarding a swimmer safety/hazard status. AnOutput to provide a pump shutdown command if a close approach by aswimmer near a drain is measured, A housing for the Transmitter andReceiver, Logic and Control that can be located in the pool equipmentarea, near the pump inlet piping. A transducer mounting and interfaceadjacent to the pump inlet suction piping for retrofit applications. Thetransducer and its interconnecting cable may be mounted in or under thedrain for new construction, or the same as for retrofit if suitable, andfor new construction, and in some cases for retrofit, other suction sidepiping and fittings that optimize performance may be used instead of theSchedule 40 90 degree elbow that has been the standard for some time.PVC piping will be used but as we are dealing with suction sidepressures the use of Schedule 40 pipe should not be a necessarylimitation.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings constitute a part of this specification and includeexemplary embodiments to the invention, which may be embodied in variousforms. It is to be understood that in some instances various aspects ofthe invention may be shown exaggerated or enlarged to facilitate anunderstanding of the invention.

FIG. 1A is a Pool Shell Section with Swimmer and Drain

FIG. 1B is a Swim By Time History

FIG. 1C shows Swimmer Drain Approach Trajectories

FIG. 1D depicts Range Cells to Catagorize the Hazard Status

FIG. 2 A,B,C Alternate Ultrasonic Transducer Feeds

FIG. 3 Preferred New Construction Drain Detail

FIG. 4 A,B Block Diagrams for Remote Transducer/Launcher

FIG. 5 Detail of Preferred Retrofit Modification

FIG. 6 Detail of Replaceable Transducer for Retrofit

FIG. 7 A,B,C Propagation Test Data for Drain Cover and Hand

FIG. 8A Drain Cover and Hand in NO-GO gate

FIG. 8B Sweep Elbow Test Data

FIG. 8C U Tube Water Echo at 200 kHz

FIG. 9 Simplified Propagation Model

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Detailed descriptions of the preferred embodiment are provided herein.It is to be understood, however, that the present invention may beembodied in various forms. Therefore, specific details disclosed hereinare not to be interpreted as limiting, but rather as a basis for theclaims and as a representative basis for teaching one skilled in the artto employ the present invention in virtually any appropriately detailedsystem, structure or manner.

FIG. 1A shows the pool 10 containing water 11 a drain 16 a drain cover14 and a suction pipe 12 that leads to the pump inlet (not shown here).Also a swimmer 18 encounters the sensor waves 19 emitted through thedrain cover 14. Reflection echoes 20 are produced by the swimmer 18 andthe water level 11.

FIG. 1B is an analysis of the range from the drain verus time as aswimmer passes by. shown are the range gates considered as safe “OK” andunsafe “No-Go”.

FIG. 1C emphasizes the rate of approach to a drain by a swimmer, andtherefore a transition from safe to unsafe.

FIG. 1D defines several additional range cells or gates, so that logicaldecisions can be implemented to protect swimmers while minimizing thefalse alarm rate.

FIG. 2A is a detail of a drain 16 and feed pipe 12 that is acting as awaveguide for the ultrasonic waves 15 generated remotely. Likewise theechoes returned 17 are transferred to the remote transducer. Thisrepresents the preferred embodiment but in some retrofit installationsit may not perform optimally. In this situation alternatives shown inFIGS. 2B and 2C would allow a transducer 30 to connect via a cable 32 ora launcher 28 to connect via a thin plastic tube ultrasonic waveguide26.

FIG. 3 is a detail of the preferred embodiment for new construction. Thedrain 16 is used as a housing for the transducer or launcher 17, wherethe thansducer or launcher may be installed within the drain 16 on topof the bottom surface 19, or underneath the bottom 19 so that thetransducer 17 need not be continuously immersed, If the transducer 17 isexternal to the drain bottom 19 it must be acoustically bonde to radiateperpendicularly to the bottom 19 and send waves through the cover to thewater beyond. A conduit 21 houses and protects the feed cable or thinplastic waveguide 20 to the aboveground Transmit/Receive unit 22. Suchan arrangement provides the most options for frequency and minimizes theattenuation problem, that occurs at higher frequencies, (See FIG. 9)thus offering the best Small Target Detectability that is available.

FIG. 4A is a block diagram for the use of a remote transducer with acable feed. The transducer 17T is connected via cable 20C to the T/Runit 22 which is then connected to the Logic and Control unit 35. Innormal operation, the L/C 35 sends an OK signal to the Alarms andIndicator 40 and a Green light will be displayed for the system status.When a Pump Shutdown is deemed necessary the UC unit 35 interrupts thePump Cpntrol Signal 37, disconnecting the Pump from Power Source 38.Then the L/C unit 35 sends a No-Go signal to the A/I unit 40, the statuslight changes from green to red, and various alarms are sounded bothlocally and, if desired, remotely.

FIG. 4B is the same as 4A with the change of location for the transducer17T and the addition of a Launcher 17L and waveguide 20WG.

FIG. 5A shows the physical arrangement of a typical pump and inlet sidepiping 53 and elbow fitting 54 leading to the underground pool drain,before modification.

FIG. 5B shows the preferred modification for retrofir applicationswherin the suction side piping 53 is used a a waveguide for theultrasonic pulses transmitted 57 and the echoes received 58. Thetransducer housing 55 connects to the Transmitter/Receiver unit 22 viacable 20C. The main modification is seen to involve removing the 90degree elbow 54 and reconnecting the piping 53 with a standard T fittingthat will both restore the water path and enable the unrestrictedultrasonic waves 57 and 58 to connect with the transducer in housing 55.

FIG. 6 provides some detail on the means for installing a replaceableTransducer/Launcher 52 under the bottom of a drain 16. Again, a conduit53 is arranged to connect the transducer/launcher 52 with an appropriatecable or waveguide to the aboveground Transmitter/Receiver 22. Thisarrangement appears to be useful principally for new construction but,depending on circumstances could be adapted to retrofits as well.

FIG. 7A shows echo data at 2 frequencies for a Hayward Drain Cover whichis typical of both new construction and retrofit situations. A largerand more defined echo was obtained at 660 kHz compared with 1 mHz, butboth are quite acceptable.

FIG. 7B shows echo data at 1 mHz. In FIG. 7B-1 there is only a draincover present.

The next FIG. 7B-2, contains the echo of a persons hand as well as thedrain cover.

The last FIG. 7B-3 shows a 10× magnification of the horizontal timescale at the hand echo and we can see distinct groups of echo pulses.This my be due to more than one finger reflection or th hand orientationbut it provides a charateristic “signature” which is useful for objectclassification purposes.

FIG. 7C shows the use of range gates to sort the hazard level based ondistance from a drain. FIG. 7C-1 shows the drain cover echo within arange cell gate that would be the normal condition. FIG. 7C-2 againshows the drain cover echo and the Close Swimmer Range Cell. An echo inthis cell would call for an immediate pump shutdown. This cell as shown,has an extent in range of about 15 inches beginning at the drain cover.FIG. 7C-3 shows a drain cover echo and a Far Swimmer Range Cell thatbegins at the end of the Close Swimmer Range Cell and extends forseveral feet. This cell is for monitoring swimmer activity and would notcall for an immediate pump shutdown, but could be used to generate anwarning/alarm signal when this cell is occupied.

FIG. 7C-4 is an example of a very high resolution test with a 3.5 mHzplastic film transducer. The middle echo is the water surface in abucket filled with 6 inches of water showing the very fine resolutionavailable for short range applications. The later right side echo is dueto a second time around reflection and is exactly twice as far away intime as the water surface echo. It should be understood that more thanone transducer can be employed in an installation and particularly fornew construction can offer the best of both options with high resolutionup close using high frequencies and longer range for distance coverageat low frequencies. This may be characterised as a dual modeconfiguration. (see also FIG. 9).

FIG. 8A shows in more detail echo data for the Drain Cover and a Handabout 5 inches from the cover and in a No-Go gate. We also can see inthe lower panel of FIG. 8A the real time FFT display for the hand echo.This illustrates the signal to noise improvement that can be realizedwith the equivalent of a matched filter or correlation.

FIG. 8B shows the reduction in attenuation with a long sweep elbowcompared with a conventional 90 degree Schedule 40 elbow.

FIG. 8C shows the improvement that can occur at some lower frequencies,in this case 200 kHz. All echoes are clearly identified for this U Tubetest.

FIG. 9 is a simplified propagation model to show the general trends thatrelate frequency with relative attenuation and relative small targetdetectability. In general the higher the frequency the greater theattenuation, and the better the detectability providing that an adequateS/N ratio can be maintained. Likewise, lower frequencies suffer lessattenuation but also do not detect small targets very well. In additionto this simplified model the literature shows many examples of whatmight be considered anomalous departures from the trend lines, but whichare in reality cyclic variations in attenuation, perhaps due to specificpropagation modes in a structure, that offer low loss windows. One mustcarefully choose the optimum frequencies for a system design. In thisregard U.S. Pat. No. 5,289,436 Ultrasonic waveguide, J. H. Terhune,offers some interesting examples of low loss frequency windows in thintubular structures.

While the invention has been described in connection with a preferredembodiment, it is not intended to limit the scope of the invention tothe particular form set forth, but on the contrary, it is intended tocover such alternatives, modifications, and equivalents as may beincluded within the spirit and scope of the invention as defined by theappended claims.

1. A machine for Anticipatory Sensing and Intervention (ASI) to avoidswimmer entrapment in new pool construction, using the suction piping asa waveguide, for use with a swimming pool and/or spa or whirlpoolhydraulic system, wherein said hydraulic system includes at least onepool pump having inlet and outlet lines, a pool drain line, at least onepool main drain, and a pump control contactor and/or SVRS, said ASIcomprising: An active suction entrapment sensor (e.g. ultrasonic) thatcan assess the relative hazard based on swimmer proximity to the draincover; An Ultrasonic Transducer, one or more, to launch waves into thesuction piping and/or drain system, and to receive echoes from the draincover; swimmer limbs, hair or body; and the pool or water surfaceparallel to the drain cover; the mounting should be coaxial with thepipe to maintain axi-symmetry for the best ultrasonic wave performance;A Transmitter/Pulser to electrically energize said ultrasonic transducerto launch waves into the suction piping and drain system; AReceiver/Processor to detect the echoes electrical signals from the saidultrasonic transducer, and to receive echoes from objects of interestbeyond the pool drain, including but not limited to, the drain cover, aswimmer's body or limb, or long hair in close proximity to the drainand/or cover, and the pool or water surface parallel to the drain cover;A Logic and Control element to convert the detected signals intoreliable information regarding a swimmer safety/hazard status; An Outputto provide a pump shutdown command if a close approach by a swimmer neara drain is measured; A housing for the Transmitter and Receiver, Logicand Control that can be located in the pool equipment area; A transducermounting and cable adjacent to the pump inlet suction piping; and Othersuction side piping and fittings that optimize performance, such assweep elbows, will be used instead of the standard Schedule 40, 90degree elbows, for the waveguide mode. Alarms, both local and remote,are important to alert operating personnel to a hazardous condition,visible and audible types are used; Self calibration and self test areboth available because the normal pool water level remains within afairly narrow renge such that the surface echo range from thetransducer, or drain cover, is accurately known, the presence of thewater surface echo is important to assure the system normal operation;Water velocity is available from doppler or time-of-flight measures forthe waveguide installations; and A pool alarm to respond to a personfalling into the water is also inherent in the design because thetransducers can act in a passive mode as well.
 2. The machine forAnticipatory Sensing and Intervention (ASI) to avoid swimmer entrapmentin new pool construction, using the suction piping as a waveguide, asclaimed in claim 1, wherein the transducers for waveguide feed arereplaceable, and can be housed in a manner to allow for normal immersionor dry operation by means of bonding behind a thin plastic window incontact with the suction waterflow.
 3. The machine for AnticipatorySensing and Intervention (ASI) to avoid swimmer entrapment in new poolconstruction, using the suction piping as a waveguide, as claimed inclaim 1, wherein a means of venting air from the transducer housing isprovided.
 4. The machine for Anticipatory Sensing and Intervention (ASI)to avoid swimmer entrapment in new pool construction, using the suctionpiping as a waveguide, as claimed in claim 1, wherein Ultrasonictransducers may be piezoelectric, ferromagnetic, electromagnetic,plastic film, crystal, ceramic or others.
 5. The machine forAnticipatory Sensing and Intervention (ASI) to avoid swimmer entrapmentin new pool construction, using the suction piping as a waveguide, asclaimed in claim 1, wherein CW, Spread Spectrum, FM, Tone Burst, SquareWave, Impulse and other forms of transducer excitation can beconsidered.
 6. The machine for Anticipatory Sensing and Intervention(ASI) to avoid swimmer entrapment in new pool construction, using thesuction piping as a waveguide, as claimed in claim 1, wherein means forimproving the S/N ratio and detectability can include passbandfiltering, matched filtering, correlation, integration, FFT, phaselocking, and others; both analog and digital.
 7. A machine forAnticipatory Sensing and Intervention (ASI) to avoid swimmer entrapmentin new pool construction, using the drains to house the sensortransducer, for use with a swimming pool and/or spa or whirlpoolhydraulic system, wherein said hydraulic system includes at least onepool pump having inlet and outlet lines, a pool drain line, at least onepool main drain, and a pump control contactor and/or SVRS, said ASIcomprising: An active suction entrapment sensor (e.g. ultrasonic) thatcan assess the relative hazard based on swimmer proximity to the draincover; An Ultrasonic transducer, one or more, to launch waves into thedrain, and to receive echoes from the drain cover, swimmer limbs, hairor body, and the pool or water surface parallel to the drain cover; ATransmitter/Pulser to electrically energize said ultrasonic transducerto launch waves into the drain and cover; A Receiver/Processor to detectthe echoes electrical signals from the said ultrasonic transducer, andto receive echoes from objects of interest beyond the pool drain,including but not limited to, the drain cover, a swimmer's body or limb,or long hair in close proximity to the drain and/or cover, and the poolor water surface parallel to the drain cover; A Logic and Controlelement to convert the detected signals into reliable informationregarding a swimmer safety/hazard status; An Output to provide a pumpshutdown command if a close approach by a swimmer near a drain ismeasured; A housing for the Transmitter and Receiver, Logic and Controlthat can be located in the pool equipment area; A transducer mountingand cable, or in or under at least one main drain; A main drain that hasbeen modified with a removeable mounting provision for thetransducer/cable assembly; A conduit from the pool equipment pad tohouse and allow replacement of the transducer and cable assembly;Alarms, both local and remote, are important to alert operatingpersonnel to a hazardous condition, visible and audible types are used;Self calibration and self test are both available because the normalpool water level remains within a fairly narrow renge such that thesurface echo range from the transducer, or drain cover, is accuratelyknown, the presence of the water surface echo is important to assure thesystem normal operation; Water velocity is available from doppler ortime-of-flight measures for the waveguide installations; and A poolalarm to respond to a person falling into the water is also inherent inthe design because the transducers can act in a passive mode as well. 8.A machine for Anticipatory Sensing and Intervention (ASI) to avoidswimmer entrapment in new pool construction, using the drains to housethe sensor transducer, as claimed in claim 7 the transducers arereplaceable, and can be housed in a manner to allow for normal immersionor dry operation by means of bonding behind a thin plastic window incontact with the suction waterflow.
 9. The machine for AnticipatorySensing and Intervention (ASI) to avoid swimmer entrapment in new poolconstruction, using the drains as claimed in claim 7, wherein ahydrophone can be integrated into the transducer housing for the purposeof improving swimmer detection, is provided.
 10. The machine forAnticipatory Sensing and Intervention (ASI) to avoid swimmer entrapmentin new pool construction, using the drains, as claimed in claim 7wherein Ultrasonic transducers may be piezoelectric, ferromagnetic,electromagnetic, plastic film, crystal, ceramic or others.
 11. Themachine for Anticipatory Sensing and Intervention (ASI) to avoid swimmerentrapment in new pool construction, using the drains, as claimed inclaim 7, wherein CW, Spread Spectrum, FM, Tone Burst, Square Wave,Impulse and other forms of transducer excitation can be considered. 12.The machine for Anticipatory Sensing and Intervention (ASI) to avoidswimmer entrapment in new pool construction, using the drains, asclaimed in claim 7, wherein means for improving the SIN ratio anddetectability can include passband filtering, matched filtering,correlation, integration, FFT, phase locking, and others; both analogand digital.
 13. A machine for Anticipatory Sensing and Intervention(ASI) to avoid swimmer entrapment, for retrofit pool installation usingthe suction piping as a waveguide, for use with a swimming pool and/orspa or whirlpool hydraulic system, wherein said hydraulic systemincludes at least one pool pump having inlet and outlet lines, a pooldrain line, at least one pool main drain, and a pump control contactorand/or SVRS, said ASI comprising: An active suction entrapment sensor(e.g. ultrasonic) that can assess the relative hazard based on swimmerproximity to the drain cover; An Ultrasonic Transducer, one or more, tolaunch waves into the suction piping and/or drain system, and to receiveechoes from the drain cover; swimmer limbs, hair or body; and the poolor water surface parallel to the drain cover; the mounting shold becoaxial with the pipe to maintain axi-symmetry for the best ultrasonicwave performance; A Transmitter/Pulser to electrically energize saidultrasonic transducer to launch waves into the suction piping and drainsystem; A Receiver/Processor to detect the echoes electrical signalsfrom the said ultrasonic transducer, and to receive echoes from objectsof interest beyond the pool drain, including but not limited to, thedrain cover, a swimmer's body or limb, or long hair in close proximityto the drain and/or cover, and the pool or water surface parallel to thedrain cover; A Logic and Control element to convert the detected signalsinto reliable information regarding a swimmer safety/hazard status; AnOutput to provide a pump shutdown command if a close approach by aswimmer near a drain is measured; A housing for the Transmitter andReceiver, Logic and Control that can be located in the pool equipmentarea; A transducer mounting and cable adjacent to the pump inlet suctionpiping; Alarms, both local and remote, are important to alert operatingpersonnel to a hazardous condition, visible and audible types are used;Self calibration and self test are both available because the normalpool water level remains within a fairly narrow renge such that thesurface echo range from the transducer, or drain cover, is accuratelyknown, the presence of the water surface echo is important to assure thesystem normal operation; Water velocity is available from doppler ortime-of-flight measures for the waveguide installations; and A poolalarm to respond to a person falling into the water is also inherent inthe design because the transducers can act in a passive mode as well.14. The machine for Anticipatory Sensing and Intervention (ASI) to avoidswimmer entrapment in retrofit installations, using the suction pipingas a waveguide, as claimed in claim 13, wherein the transducers forwaveguide feed are replaceable, and can be housed in a manner to allowfor normal immersion or dry operation by means of bonding behind a thinplastic window in contact with the suction waterflow.
 15. The machinefor Anticipatory Sensing and Intervention (ASI) to avoid swimmerentrapment in retrofit installations, using the suction piping as awaveguide, as claimed in claim 13, wherein a means of venting air fromthe transducer housing is provided.
 16. The machine for AnticipatorySensing and Intervention (ASI) to avoid swimmer entrapment in retrofitinstallations, using the suction piping as a waveguide, as claimed inclaim 13 wherein Ultrasonic transducers may be piezoelectric,ferromagnetic, electromagnetic, plastic film, crystal, ceramic orothers.
 17. The machine for Anticipatory Sensing and Intervention (ASI)to avoid swimmer entrapment in retrofit installations, using the suctionpiping as a waveguide, as claimed in claim 13, wherein CW, SpreadSpectrum, FM, Tone Burst, Square Wave, Impulse and other forms oftransducer excitation can be considered.
 18. The machine forAnticipatory Sensing and Intervention (ASI) to avoid swimmer entrapmentin retrofit installations using the suction piping as a waveguide, asclaimed in claim 13, wherein means for improving the SIN ratio anddetectability can include passband filtering, matched filtering,correlation, integration, FFT, phase locking, and others; both analogand digital.